1. Technical Field of the Invention
The present invention relates to a CVD process for producing a thin film, in which a thin film composed of a metal or metal oxide is produced by a CVD process using an organometallic compound as a material.
2. Description of the Related Art
A chemical vapor deposition process (herein after referred to as “CVD process”) is one of techniques for the formation of a thin film generally used in the production of a thin film electrode of semiconductor apparatus, since the CVD process can advantageously produce a uniform film and is excellent in step coverage. On an increasing demand for further increasing the packaging density of circuits and electronic members in recent years, it is expected that the CVD process which can meet this requirement goes mainstream of processes for producing a thin film electrode in the future.
This CVD process is a process for producing a thin film of a metal or metal oxide by (1) a step of vaporizing a metallic compound material to yield a source gas, and (2) a step of transporting the source gas to a surface of a substrate, allowing particles of the transported material to react on the substrate to yield a metal or metal oxide, and depositing the metal or metal oxide to yield a thin film. As the metallic compound material, an organometallic compound which has a low melting point and is easy to handle is particularly used.
It is assumed that a cost for the production of a thin film by the CVD process depends on a cost of a material organometallic compound and on a ratio of the amount of organometallic compound introduced onto a surface of a substrate to the amount of the organometallic compound consumed through a reaction, that is, on utilization efficiency. Utilization efficiency in conventional CVD processes is as low as 10% or less, and most of the introduced source gas is actually treated as an exhaust gas and the organometallic compound in the exhaust gas is discarded even if the organometallic compound is in an unreacted state. Accordingly, the production cost of a thin film in such a case that the utilization efficiency is low is strongly affected by the cost of the organometallic compound under present circumstances.
However, such an organometallic compound is generally expensive as it requires a multiplicity of steps for synthesis. For example, even when the metal itself is not so expensive such as in copper, the cost significantly increases when the metal is synthetically converted into an organometallic compound. It is speculated that the production cost of a thin film by a conventional CVD process inevitably increases due to the price of the expensive organometallic compound.
Additionally, a thin film of a precious metal such as ruthenium or iridium is recently applied as a material for a thin film electrode to thereby yield a high-performance electrode. An organometallic compound of a precious metal is expected to be heavily used as a material for this purpose in the future. A precious metal is naturally a rare metal and is expensive, and its organic compound is significantly expensive. Accordingly, when a precious metal thin film is produced by a conventional CVD process, a cost for forming a film is expected to further increase.
In addition, the organometallic compound has a low melting point and is easy to handle as described above, and the use of the organometallic compound can decrease a vaporization temperature and a reaction temperature (a substrate temperature) and can efficiently produce a thin film, and is expected to be increased more than ever in the future. Even when the organometallic compound grows in demand, however, the conventional CVD process having a low utilization efficiency invites a great quantity of loss in material, and there is apprehension of resource starvation.
Accordingly, an object of the present invention is to provide a CVD process for a thin film which is low in loss of a material organometallic compound and which can reduce a production cost of a thin film when compared with a conventional CVD process for a thin film, as wall as a CVD apparatus for producing a thin film which can produce a thin film without loss of organometallic compound.